It is certain, that the art of war hath suffered great changes, almost in every age and country of the world; however, there are some maxims relating to it, that will be eternal truths, and which every reasonable man will allow.

In the early times of Greece and Rome, the armies of those states were composed of their citizens, who took no pay, because the quarrel was their own; and therefore the war was usually decided in one campaign; or, if it lasted longer, however in winter the soldiers returned to their several callings, and were not distinguished from the rest of the people.  The Gothic governments in Europe, though they were of military institution, yet observed almost the same method.  I shall instance only here in England.  Those who held lands in capite of the king, were obliged to attend him in his wars with a certain number of men, who all held lands from them at easy rents on that condition.  These fought without pay, and when the service was over, returned again to their farms.  It is recorded of William Rufus, that being absent in Normandy, and engaged in a war with his brother, he ordered twenty thousand men to be raised, and sent over from hence to supply his army;[3] but having struck up a peace before they were embarked, he gave them leave to disband, on condition they would pay him ten shillings a man, which amounted to a mighty sum in those days.

Consider a kingdom as a great family, whereof the prince is the father, and it will appear plainly that mercenary troops are only servants armed, either to awe the children at home; or else to defend from invaders, the family who are otherwise employed, and choose to contribute out of their stock for paying their defenders, rather than leave their affairs to be neglected in their absence.  The art of making soldiery a trade, and keeping armies in pay, seems in Europe to have had two originals.  The first was usurpation, when popular men destroyed the liberties of their country, and seized the power into their own hands, which they were forced to maintain by hiring guards to bridle the people.  Such were anciently the tyrants in most of the small states in Greece, and such were those in several parts of Italy, about three or four centuries ago, as Machiavel informs us.  The other original of mercenary armies, seems to have risen from larger kingdoms or commonwealths, which had subdued provinces at a distance, and were forced to maintain troops upon them, to prevent insurrections from the natives:  Of this sort were Macedon, Carthage and Rome of old; Venice and Holland at this day; as well as most kingdoms of Europe.  So that mercenary forces in a free state, whether monarchy or commonwealth, seem only necessary, either for preserving their conquests, (which in such governments it is not prudent to extend too far) or else for maintaining a war at distance.

In this last, which at present is our most important case, there are certain maxims that all wise governments have observed.